The present invention relates to an apparatus for reproducing information, and more particularly to an apparatus for reproducing information, which is adapted to optically read record information from a recording medium such as an optical disk, etc.
As an medium for recording various digital data, music information, image information, or the like, optical disks are known. Since writable optical disks among these optical disks can be subjected to write once record information on the user side, the demand therefor is being increased. The write once read optical disks of these writable optical disks are called a WORM (Write Once Read Multiple) optical disk or a DRAW (Direct Read After Write) optical disk. The write once read disks are such that information can be written thereonto only once. In this case, writing is carried out by converging a laser beam onto a recording surface to transform the laser beam to a thermal energy at the convergent point (very small area portion) to perforate the recording film by fusing action, etc. due to heat generated at that time to form signal pits, thus to write record information thereinto. At the time of this writing, record information is modulated in accordance with 4/15 modulation (.sub.15 C.sub.4 : 4 out of 15 code) method. Playback or reproduction of information thus recorded is carried out by irradiating a laser beam onto a recording track on a recording surface including signal pits formed in a manner stated above to apply photoelectric conversion to a reflected laser beam by using a photodetector to apply analog-to-digital (A/D) conversion to an electric RF signal (RF: Radio Frequency) thus provided thereafter to demodulate that digital signal by using a 4/15 decoder.